The present invention relates to a yarn end loosening apparatus having adjustable height jet nozzles each for directing a stream of air against a yarn package and a controllable air supply to selectively supply the jet nozzles with air according to the height of the yarn package.
In an automatic bobbin winder, yarn packages, which are supplied via an appropriate transport system to an unwinding position at a winding head, are rewound to cross-wound bobbins. To be able to automatically engage the starting end of the yarn of the yarn packages supplied to the winding head to a yarn grasping member of the winding head, this starting end of the yarn must be easy to grasp. So-called yarn package preparation units are known for this purpose which deposit the yarn on a defined position of the yarn package. This starting end of the yarn is then blown out of a yarn end loosening chamber by means of a jet nozzle and can then be taken up. However, such devices are not suitable for taking up again yarn ends after a yarn break on an undefined position on the yarn package surface.
U.S. Pat. No. 4,921,179 to Surkamp et al teaches a yarn supplying unit comprising a yarn end loosening chamber which surrounds the yarn package to be unwound. It comprises in its interior yarn loosening jet nozzles directed tangentially and obliquely upward for generating a current of air directed helically in the direction of unwinding of the yarn. These jet nozzles are supplied with compressed air after the yarn package replacement and after a yarn break. They extend essentially over the entire height of the yarn end loosening chamber. In the case of a relatively large yarn end loosening chamber which is also suitable for correspondingly large yarn packages, a relatively great consumption of air results thereby.
Since a bobbin winding machine must customarily be suitable for rewinding different types of yarn packages which also differ in particular in their dimensions, yarn end loosening chambers must also be used which are set for a maximum yarn package length to be processed. It is necessary, in order to loosen the starting end of the yarn, to blow on the upper tapered portion of the package.
In order to reach this yarn package area with blowing air independently of the yarn package length, all jet nozzles arranged along the yarn end loosening chamber must be operated, leading to a relatively high consumption of compressed air.